In the simplest case a gas turbine plant comprises a compressor, a combustion chamber and a turbine. Ingested air is compressed in the compressor and a fuel is then mixed therewith. The mixture is combusted in the combustion chamber, the exhaust gases from the combustion process being supplied to the turbine, by which energy is extracted from the combustion exhaust gases and converted into mechanical energy.
However, variations in fuel quality and sundry other thermal or acoustic perturbations lead to fluctuations in the quantity of heat released. At the same time an interaction takes place between acoustic and thermal perturbations which can produce increased vibrations. Thermoacoustic oscillations of this type in the combustion chambers of gas turbines—or indeed turbo machines in general—pose a problem in relation to the design and operation of new combustion chambers, combustion chamber components and burners for turbo machines of said type.
In modern-day plants the cooling medium mass flow rate is reduced in order to reduce noxious emissions. This also leads to a reduction in acoustic damping, with the result that thermoacoustic oscillations can increase. An intensifying interaction between thermal and acoustic perturbations can build up in the process which can cause the combustion chamber to be subjected to heavy stresses and lead to increasing emissions.
For this reason, in order to reduce thermoacoustic oscillations, devices such as Helmholtz resonators are used in the prior art as damping mechanisms which attenuate the amplitude of oscillations at specific frequencies.
Helmholtz resonators of this type dampen in particular the amplitude of oscillations at the Helmholtz frequency as a function of the cross-sectional surface area of the connecting tube and of the resonator volume. In most cases said Helmholtz resonators are small boxes which are individually welded on the combustion chamber wall of the gas turbine. However, this is very time-consuming, labor-intensive and expensive. Furthermore, these small boxes and their welded seam have only a very limited lifespan.